
//
// QueryableTransformer.cs
//
// Authors:
//	Roei Erez (roeie@mainsoft.com)
//	Jb Evain (jbevain@novell.com)
//
// Copyright (C) 2008 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Runtime.CompilerServices;

namespace System.Linq
{

	class QueryableTransformer : ExpressionTransformer
	{

		protected override Expression VisitMethodCall(MethodCallExpression methodCall)
		{
			if (IsQueryableExtension(methodCall.Method))
				return ReplaceQueryableMethod(methodCall);
			return base.VisitMethodCall(methodCall);
		}

		protected override Expression VisitLambda(LambdaExpression lambda)
		{
			return lambda;
		}

		protected override Expression VisitConstant(ConstantExpression constant)
		{
			var qe = constant.Value as IQueryableEnumerable;
			if (qe == null)
				return constant;
			var enumerable = qe.GetEnumerable();
			if (enumerable != null)
				return Expression.Constant(enumerable);
			return Visit(qe.Expression);
		}
		static Boolean IsQueryableExtension(MethodInfo method)
		{
			return HasExtensionAttribute(method) &&
				method.GetParameters()[0].ParameterType.IsAssignableTo(typeof(IQueryable));
		}
		static Boolean HasExtensionAttribute(MethodInfo method)
		{
			return method.GetCustomAttributes(typeof(ExtensionAttribute), false).Length > 0;
		}
		MethodCallExpression ReplaceQueryableMethod(MethodCallExpression old)
		{
			Expression target = null;
			if (old.Object != null)
				target = Visit(old.Object);
			var method = ReplaceQueryableMethod(old.Method);
			var parameters = method.GetParameters();
			var arguments = new Expression[old.Arguments.Count];

			for (Int32 i = 0; i < arguments.Length; i++)
			{
				arguments[i] = UnquoteIfNeeded(
					Visit(old.Arguments[i]),
					parameters[i].ParameterType);
			}
			return Expression.Call(target, method, arguments);
		}
		static Expression UnquoteIfNeeded(Expression expression, Type delegateType)
		{
			if (expression.NodeType != ExpressionType.Quote)
				return expression;
			var lambda = (LambdaExpression)((UnaryExpression)expression).Operand;
			if (lambda.Type == delegateType)
				return lambda;
			return expression;
		}
		static Type GetTargetDeclaringType(MethodInfo method)
		{
			return method.DeclaringType == typeof(Queryable) ? typeof(Enumerable) : method.DeclaringType;
		}
		static MethodInfo ReplaceQueryableMethod(MethodInfo method)
		{
			var target_type = GetTargetDeclaringType(method);
			var result = GetMatchingMethod(method, target_type);
			if (result != null)
				return result;
			throw new InvalidOperationException(
				String.Format(
					"There is no method {0} on type {1} that matches the specified arguments",
					method.Name,
					target_type.FullName));
		}
		static MethodInfo GetMatchingMethod(MethodInfo method, Type declaring)
		{

			foreach (var candidate in declaring.GetMethods())
			{
				if (!MethodMatch(candidate, method))
					continue;
				if (method.IsGenericMethod)
					return candidate.MakeGenericMethodFrom(method);
				return candidate;
			}
			return null;
		}
		static Boolean MethodMatch(MethodInfo candidate, MethodInfo method)
		{
			if (candidate.Name != method.Name)
				return false;
			if (!HasExtensionAttribute(candidate))
				return false;
			var parameters = method.GetParameterTypes();
			if (parameters.Length != candidate.GetParameters().Length)
				return false;
			if (method.IsGenericMethod)
			{
				if (!candidate.IsGenericMethod)
					return false;
				if (candidate.GetGenericArguments().Length != method.GetGenericArguments().Length)
					return false;
				candidate = candidate.MakeGenericMethodFrom(method);
			}
			if (!TypeMatch(candidate.ReturnType, method.ReturnType))
				return false;
			var candidate_parameters = candidate.GetParameterTypes();
			if (candidate_parameters[0] != GetComparableType(parameters[0]))
				return false;

			for (Int32 i = 1; i < candidate_parameters.Length; ++i)
				if (!TypeMatch(candidate_parameters[i], parameters[i]))
					return false;
			return true;
		}
		static Boolean TypeMatch(Type candidate, Type type)
		{
			if (candidate == type)
				return true;
			return candidate == GetComparableType(type);
		}
		static Type GetComparableType(Type type)
		{
			if (type.IsGenericInstanceOf(typeof(IQueryable<>)))
				type = typeof(IEnumerable<>).MakeGenericTypeFrom(type);
			else if (type.IsGenericInstanceOf(typeof(IOrderedQueryable<>)))
				type = typeof(IOrderedEnumerable<>).MakeGenericTypeFrom(type);
			else if (type.IsGenericInstanceOf(typeof(Expression<>)))
				type = type.GetFirstGenericArgument();
			else if (type == typeof(IQueryable))
				type = typeof(IEnumerable);
			return type;
		}
	}
}
